Researchers have analyzed 141 drinking water wells across the Appalachian Plateaus of northeastern Pennsylvania, correlating natural gas concentrations and isotope signatures with proximity to shale gas wells subjected to hydraulic fracturing. Their data, published in the Proceedings of the National Academy of Sciences last week, suggest that people who live less than 1 km from gas wells may have drinking water contaminated with hydrocarbons that escaped from the wells (2013, DOI: 10.1073/pnas.1221635110). Methane was detected in 82% of drinking water samples, with an average concentration six times as high for homes less than 1 km from natural gas wells than for those farther away. And the ethane concentration was 23 times as high in water at homes less than 1 km from gas wells than at those farther away, say researchers from Duke University, the University of Rochester, and California State Polytechnic University, Pomona. Their work expands on a 2011 study that also found greater levels of methane in drinking water wells in northeastern Pennsylvania near Marcellus Shale gas wells. The earlier study was challenged by industry.